astTransformer not doing the transformations

[acalvo]

🐛 Bug Report

After seeing #2831 I tried to set a (simple) astTransformer in pure JS with no luck. Not sure if I'm hitting a bug or I misunderstood something. I made a minimal repo (based in the one from that issue, thanks for the boilerplate):

https://github.com/acalvo/ts-jest-ast-transformer

Use case:

• This is the code to test: https://github.com/acalvo/ts-jest-ast-transformer/blob/master/src/foo.ts . It has import.meta.url which is not supported when running jest with that config (error The 'import.meta' meta-property is only allowed when the '--module' option is 'es2020', 'esnext', or 'system'.).
• If it was (for example) 'http://localhost/' instead of import.meta.url, Jest would run correctly, so I want to make that transformation.
• This is the AST transformer in pure JS (converted from TS): https://github.com/acalvo/ts-jest-ast-transformer/blob/master/plugin/transformer.js

To Reproduce

git clone https://github.com/acalvo/ts-jest-ast-transformer.git
npm install
npm start

Expected behavior

I'd expect the transformation (import.meta.url -> 'http://localhost/') to apply, and the test to pass.

Instead, the test fails because the unsupported import.meta.url is still there.

Link to repo (highly encouraged)

https://github.com/acalvo/ts-jest-ast-transformer

Debug log:

-

envinfo

System:
    OS: macOS 11
    Node version: v14.17.1

Npm packages:
    jest: 27.2.1
    ts-jest: 27.0.5
    typescript: 4.4.3
    babel(optional): -

Thanks!!

[ahnpnl]

Hi, if you run jest with no-cache, do you see your transformer code hit debug point?

[ahnpnl]

Hi, I've checked your repo. Your transformer works correctly. However, type checking process in TypeScript doesn't perform on the js output but it runs on original ts, which explains why you still get the error

error TS1343: The 'import.meta' meta-property is only allowed when the '--module' option is 'es2020', 'esnext', or 'system'.

Note that custom AST transformers only affects how you want your js to be. It doesn't affect on type checking process